Centrifugal fan

ABSTRACT

A centrifugal fan includes a housing including an air collecting portion, a first frame and a second frame. The air collecting portion has an air outlet defined in one end thereof. The first and second frames are located at two opposite sides of an opposite end of the air collecting portion. The first and second frames each define a receiving space therein for rotatably receiving an impeller. The first and second frames each further define a vent hole therein. The receiving spaces of the first and second frames communicate with the inner space of the air collecting portion via the vent holes thereof. Airflow generated by the two impellers travels to the inner space of the air collecting portion through the vent holes of the first and second frames, and exits the centrifugal fan through the air outlet of the air collecting portion.

BACKGROUND

1. Technical Field

The present disclosure generally relates to heat dissipation, and particularly to a centrifugal fan for dissipating heat from electronic components.

2. Description of Related Art

With developments in technology, improved performance of electronic components such as CPUs (central processing units) has been achieved. However, such electronic components generate increased levels of heat, which must be dissipated promptly. Conventionally, a centrifugal fan is used to remove the generated heat of the electronic components.

The centrifugal fan includes a housing and an impeller rotatably mounted in the housing. The housing defines an air outlet and an air inlet perpendicular to the air outlet. In operation, air outside the housing of the centrifugal fan is pumped into the housing via the air inlet thereof and then expelled out of the housing by the impeller from the air outlet to take away the generated heat of the electronic component. The efficiency of the centrifugal fan is proportionate to an airflow volume and an airflow pressure of the centrifugal fan. To increase airflow volume and pressure, the rotation speed of the centrifugal fan can be increased. However, such an increase normally also increases noise generated by the centrifugal fan.

Therefore, what is needed is a centrifugal fan which can overcome the described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric, assembled view of a first embodiment of a centrifugal fan.

FIG. 2 is an exploded view of the centrifugal fan of FIG. 1.

FIG. 3 is an isometric, assembled view of a second embodiment of a centrifugal fan.

FIG. 4 is an isometric view of a housing of the centrifugal fan of FIG. 3.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a first embodiment of a centrifugal fan is shown. The centrifugal fan 100 includes a hollow housing 10, and a first impeller 20 and a second impeller 30 each rotatably mounted in the housing 10.

The housing 10 includes an air collecting portion 40, and a first frame 50 and a second frame 60 both connected at a rear of the air collecting portion 40. The first frame 50 and the second frame 60 are symmetrically disposed at two lateral sides of the rear of the air collecting portion 40. An air outlet 41 is defined in the front of the air collecting portion 40.

The air collecting portion 40 includes a bottom plate 42, a top plate 43 and two guide plates 44 connected between the bottom plate 42 and the top plate 43. The bottom plate 42 faces the top plate 43. The two guide plates 44 are located at two opposite lateral sides of the bottom plate 42, and are parallel to each other. A cross section of the air collecting portion 40, taken in a vertical plane, is rectangular.

The first and second frames 50, 60 each have a generally round profile. The first frame 50 defines a first receiving space 51 therein for rotatably receiving the first impeller 20, and the second frame 60 defines a second receiving space 61 therein for rotatably receiving the second impeller 30.

The first frame 50 further defines a first vent hole 52 therein near the rear of the air collecting portion 40, and the second frame 60 further defines a second vent hole 62 therein near the rear of the air collecting portion 40. The first vent hole 52 and the second vent hole 62 each communicate with the inner space of the air collecting portion 40. Airflow generated by the first impeller 20 and the second impeller 30 is guided and collected via the first and second vent holes 52, 62 to the inner space of the air collecting portion 40, and then exits the centrifugal fan 100 from the air outlet 41 of the air collecting portion 40. An area of the air outlet 41 is less than a total area of the first vent hole 52 and the second vent hole 62.

Each of the first frame 50 and the second frame 60 includes a supporting plate 71, a cover plate 72, and a volute side plate 73 connecting between the supporting plate 71 and the cover plate 72. The side plate 73 extends upwardly and perpendicularly from an outer periphery of the supporting plate 71. The first vent hole 52 is defined in the side plate 73 of the first frame 50, and the second vent hole 62 is defined in the side plate 73 of the second frame 60. The cover plates 72 of the first frame 50 and the second frame 60 each define an air inlet 74 therein. The air inlets 74 of the first frame 50 and the second frame 60 are located above and concentric with the first impeller 20 and the second impeller 30, respectively.

A rear end of the side plate 73 of the first frame 50 connects with a rear end of the side plate 73 of the second frame 60 to form a connecting portion 75 at a rear of the air collecting portion 40. The connecting portion 75 is located between the first impeller 20 and the second impeller 30, and an end face of the connecting portion 75 faces the center of the air collecting portion 40. Front ends of the side plates 73 of the first frame 50 and the second frame 60 are spaced apart from each other, and connect with rear ends of the two guide plates 44 of the air collecting portion 40, respectively.

Each of the first impeller 20 and the second impeller 30 includes a cylindrical hub 21 and a plurality of blades 22 extending tangentially from the periphery of the hub 21. The hubs 21 of the first and second impellers 20, 30 are rotatably mounted on the supporting plates 71 of the first and second frames 50, 60, respectively. Each of the blades 22 is a straight strip-shaped plate and perpendicular to the supporting plate 71. A distance between the first impeller 20 and the air outlet 41 of the air collecting portion 40 is equal to that between the second impeller 30 and the air outlet 41 of the air collecting portion 40.

During operation of the centrifugal fan 100, a rotation direction of the first impeller 20 is different from (i.e., opposite to) that of the second impeller 30. In this embodiment, the first impeller 20 rotates clockwise and the second impeller 30 rotates counterclockwise. Air is drawn into the housing 10 through the two air inlets 74 of the cover plates 72 of the first frame 50 and the second frame 60, and the resulting airflow is accelerated and expelled by the first impeller 20 and the second impeller 30 out of the first frame 50 and the second frame 60 via the first and second vent holes 52, 62 towards the inner space of the air collecting portion 40. Airflow from the first frame 50 and the second frame 60 is combined in the air collecting portion 40, and exits the centrifugal fan 100 from the air outlet 41 of the air collecting portion 40.

In the centrifugal fan 100, airflow is driven by the first impeller 20 and the second impeller 30, and airflow from the first frame 50 and the second frame 60 is combined in the air collecting portion 40, such that airflow out of the air outlet 41 of the air collecting portion 40 has high volume and pressure. Such high volume and pressure can be achieved even when the first and second impellers 20, 30 of the centrifugal fan 100 rotate at a relatively low speed, thus providing efficient operation with reduced noise. In this embodiment, the first and second impellers 20, 30 rotate at the same speed. Understandably, the first and second impellers 20, 30 can instead rotate at different speeds to provide an adjustable volume and pressure.

FIGS. 3 and 4 show a second embodiment of a centrifugal fan 100 a. The centrifugal fan 100 a differs from the centrifugal fan 100 of the previous embodiment only in that a first frame 50 a and the second frame 60 are arranged at two opposite sides of a rear of the air collecting portion 40 a in an asymmetrical manner. That is, the first frame 50 a is closer to the air outlet 41 of the air collecting portion 40 a than the second frame 60. The first impeller 20 is closer to the air outlet 41 of an air collecting portion 40 a than the second impeller 30, and a guide plate 44 a of the air collecting portion 40 a which connects with the side plate 73 of the first frame 50 a is shorter than the guide plate 44 of the air collecting portion 40 a which connects with the side plate 73 of the second frame 60. In operation of the centrifugal fan 100 a, an average angle of airflow out of a first vent hole 52 a of the first frame 50 a is different from that of the airflow out of the second vent hole 62 of the second frame 60, thus reducing noise generated by resonance of airflow. Furthermore, airflow from the second vent hole 62 is accelerated by airflow from the first vent hole 52 a, increasing airflow pressure of the centrifugal fan 100 a.

It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A centrifugal fan comprising: a housing comprising an air collecting portion, the air collecting portion having an air outlet defined in one end thereof; a first frame and a second frame adjacent two opposite lateral sides of an opposite end of the air collecting portion, respectively, the first frame defining a first receiving space and a first vent hole therein, the second frame defining a second receiving space and a second vent hole therein, the receiving spaces of the first frame and the second frame communicating with an inner space of the air collecting portion via the first vent hole and the second vent hole, respectively; and a first impeller rotatably received in the first receiving space and a second impeller rotatably received in the second receiving space; wherein airflow generated by the first impeller is guided to the inner space of the air collecting portion via the first vent hole, airflow generated by the second impeller is guided to the inner space of the air collecting portion via the second vent hole, and resulting airflow at the air collecting portion is expelled out of the centrifugal fan through the air outlet of the air collecting portion.
 2. The centrifugal fan of claim 1, wherein the air collecting portion comprises a bottom plate, a top plate and two guide plates connected between the bottom plate and the top plate.
 3. The centrifugal fan of claim 2, wherein the two guide plates are parallel to each other, and a cross section of the air collecting portion taken along a plane spanning from the top plate to the bottom plate is rectangular.
 4. The centrifugal fan of claim 3, wherein each of the first frame and the second frame comprises a supporting plate, a cover plate, and a volute side plate connecting between the supporting plate and the cover plate, the first vent hole is defined in the side plate of the first frame, the second vent hole is defined in the side plate of the second frame, and the cover plates of the first frame and the second frame each define an air inlet therein.
 5. The centrifugal fan of claim 4, wherein a rear end of the side plate of the first frame connects with a rear end of the side plate of the second frame to form a connecting portion between the first and second impellers, and front ends of the side plates of the first frame and the second frame respectively connect with rear ends of the two guide plates of the air collecting portion.
 6. The centrifugal fan of claim 5, wherein the connecting portion is outside the air collecting portion and faces the center of the air collecting portion.
 7. The centrifugal fan of claim 1, wherein the first frame and the second frame are symmetrically disposed at the two opposite lateral sides of the opposite end of the air collecting portion.
 8. The centrifugal fan of claim 1, wherein the first frame and the second frame are arranged at the two opposite sides of the opposite end of the air collecting portion in an asymmetrical manner, with the first frame being closer to the air outlet of the air collecting portion than the second frame.
 9. The centrifugal fan of claim 1, wherein an area of the air outlet is less than a total area of the first vent hole and the second vent hole.
 10. The centrifugal fan of claim 1, wherein the first and second impellers rotate in opposite directions. 